1. Field of the Invention
The present invention relates to an exhaust gas-purifying system for internal combustion engines, which has at least one catalyst arranged in an exhaust passage of the engine, for purifying exhaust gases from the engine.
2. Prior Art
An exhaust gas-purifying system for internal combustion engines has been proposed by Japanese Provisional Utility Model Publication (Kokai) No. 4-105925, which includes a heater-equipped catalyst arranged in an exhaust passage of the engine, which operates to heat the catalyst for acceleration of activation thereof when the engine is started in a cold condition.
However, in the conventional system it takes a fairly long time to heat the catalyst to an activation temperature at or above which it is activated, by the heater alone. To shorten the required heating time period for prompt activation of the catalyst, a heater having a large capacity is required, which, however, necessitates the use of a battery having an increased size for supplying electric power to the heater, resulting in an increased cost, etc.